Natural horizon simulating device for training purposes



July 5, 1949. w. w. WOOD, JR., ETAL 2,475,366

NATURAL HORIZON SIMULATING DEVICE FOR TRAINING PURPOSES Filed March '15, 194-5 4 Sheets-Sheet 1 WILLIAM W. \NOOD, JR

GUNNE LOWKRANTZ INVENTOR 7% ATT NEYS July 5,, 1949. w. w. WOOD, JR, ET AL 2,475,366

NATURAL HORIZON SIMULATING DEVICE FOR TRAINING PURPOSES Filed March 15, 1946 4 Sheets-Sheet 2 5&2- /07 m9 F|G.8

Q (D D NVENTOR AfTO W49, w. w. WOOD, JR, ETAL 2,475,366

NATURAL HORIZON SIMULATING DEVICE FOR TRAINING PURPOSES Filed March 15, 1946 4 Sheets-Sheet 3 206 I L 206 v a lqa-i flio moa M06 M0 226 FIG. I? na @/7a@ WILLIAM W. WOODJR.

GUNNE LOWKRANTZ INVENTOR (23/ 4mm ATTO EYS NATURAL HORIZON SIMULATING DEVICE .Iufly 5, 1949. w w. WOOD, JR., ETAL 2,475,366

FOR TRAINING PURPOSES Filed March 15, 1946 4 Sheets-Sheet 4 WILLIAM W. WOODJR. GUNNE LOWKRANTZ BY%M/ Patented July 5, 1949 UNITED STATES NATURAL nonrzon SIMULA'HN'G DEVICE FOR TRAINING PURPOSES WilliaiiiW. Wood, .lr.', Staten Island; and during li ovvltrantz, Binghamton, N. Y assignors to Link Aviation, Inc a corporation'of'Ne'w 'Yo'rk Application March 15, 1946, Sliflil NOf654fi74 "1 claims: (01188 -13 This invention in it'sbroa'clest'aspectsrelates t'o' leveling. devices, and more particularly is concern'ed with a leveling device for use in'leveling sighting instruments. It will be illustrated in connection-with its use 'for leveling instruments such as'sextants while taking observations upon real or simulated celestial bodies.

It is well knownby' those skilled in the art of celestial navigation that certain types of sex tants commonly referredto as marine sextants employ a'horizon viewing arrangement whereby the observer may sight the distant horizon and manipulate the index"mirror of the sextant until the'image of the celestial body being observed bears a predetermined relation to the image of the viewed horizon. By observing the reading ofthe instrumentan'd by making the necessary conventional corrections, such as for index error, dip, etc., the altitude of the celestial body being observed may be ascertained.

Our invention relates to an artificial device whichma'y be employed to be viewed by the user of the sextant to level the instrument, instead'of employing the real horizon, whereby valuable training may be secured in the use of a marine type sextant, or similar instrument.

The apparatus to be disclosed may be installed upon the ground for use in taking practice ob servations upon the stars or planets, it may be used in conjunction with a single collimatorar ranged to represent the position of a celestial body, or it may be used in conjunction with celestial navigation trainers of the type disclosed and claimed in U. S. Patent 2,364,539 issued to Edwin A. Link. Other uses may also be found.

Essentially, the device to bedescribed comprises a suitable light source, an image bearing member, a transparent reflector and a collimating system, all optically arranged to provide a suitable image to be viewed by the user of the sextant for leveling the instrument. The collimating' system places the viewed image'optical 1y at infinity. The just mentioned apparatus is enclosed in a suitable housing which is mounted in a gimbal ring for movement about one axis, the gimbal ring in turn being mounted'for movement about an axis at right angles to the first axis, in order that the device may be placed in exactly the desired position. Novel means for balancing the collimator assembly will also be disclosed, as Well as many other important features of our invention.

In order that'the" exact nature of our device may be better understood, reference'is madeto the accompanying drawings, wherein,

Fig? 1 is a perspective View of the exterior of the; collimator assembly.

Fig. lA'is a cross secti onal-view of the collimator'and platform riioiir'itijngbase l Fig. 2 is a top viewoi'tn collimator assmbly Fig 3' is 'a' eispeetive'view of on'e'of' the bearing "assemblies;

Fig. 8 -is a; diagrammatic View showing the relative positions of the'optical-n'iembers.

Fig. -9 -is-a top view-of the horizon; plate. 7

Figs; l0 and 10A-show--the"opt-ical principles of this invention-.--

Figs 11 showsthe-viewseen by an observer.

Fig. 12 is a wiring diagram of-the lighting system-.

Figa' l3 shows the arrangement for simulating the taking :of observations from diiierent heights" above the water:

Fig:- l l'nllustrates the subject" matter of this invention as us'ed--in conjunetiomwith the previous mentioned celestial navigation trainers, and;

Fi'gl ls' illustrates meansmrdedicating the assumed heading of a ship u'po'n which an-observer is assumed T to be ldeate'di mg-nibunteaupon we ton tfie pilitrrm' zt having zsana bessetcigtrispmms i; spleen-l2 is rigidly held bythef three-answers inemen-supporting" members "I 3 which attacli tmthe spindle and to three*ofthe horiontalfniinbersI l. A'sl e've'M is providedi andit; should-be teamma this sleeve is completely is ntanamspiaaie 1 2; sleeve" 1 4 its:

members to "weather-three"horizontal niembers' l. In:

tegfal with "sleeve 1'4 is the must "I a 1 which sup:

ports the inner raee r the earing assembly clesigfiatdgefierally by 11. The "outer" race of this assembly supports the internal ring 38a integral with housing 38, and ring 38a in turn supports the upper bearing assembly I8. The shouldered collar I 9 rests upon bearing assembly I8, and supports the insulating ring 28- which carries the two slip rings 2|. A brush block 22 is fixedly held by screws 22a to the housing 38, and in turn supports the two brushes 23, each of which is arranged to bear against one of the slip rings 2| for the transfer of electrical energy, as is well known. Aflixed to the housing 38 are the two horizontal members 28, and a plurality of counterbalancing weights 32 rest upon one end of the horizontal members 28.

Aflixed to the rear end of each of the members 28 is one of the horizontal members 36 to which in turn are affixed the upright members 38. A pair of angularly inclined members 39 are afixed to the horizontal members 28 and to the uprights 38 in order to impart additional support to the uprights.

A pair of blocks 48 and 42 are affixed to the uprights 38, and to the blocks is afiixed the guard 44 which completely surrounds the lower part of the collimator assembly designated generally by 46. Upon the top of each of the uprights 38 is afiixed a block 48, and each of these blocks assists in supporting the upper fixed guard 58 which also circles the collimator assembly 46.

A plurality of struts 52 are afilxed to the uprights :a

38, to the guard 44, and to the blocks 48 in order to assist in supporting the collimator assembly 46. A handle 54 is afiixed to the left upright 38 in order that an observer, standing upon the platform 26, may swing the uprights 38 and the entire collimator assembly 46, as well as all other parts connected to the uprights 38, about a vertical axis through the fixed spindle I2, the bearings I1 and I8 permitting the same. The isolation of spindle I2 from sleeve I3 prevents any movements of the collimator assembly as a result of movements of the observer upon platform 26. The purpose of rotatably mounting the collimator assembly 46 in this fashion will become later apparent.

In Fig. 1 it will be seen that the collimator assembly 46 comprises a main housing designated generally by 56. The front side of this housing is 56a, the left side 561), the rear side 560, the

right side 5611, the top 56e and the bottom 56), I

as shown in Figs. 1 and 6. A window 58 is placed in front 56a. Other detailed parts upon the outside of housing 56 are shown, and they will be later described in detail.

Reference is now made to Fig. 2 which is a top view of the collimator assembly 46 and of the elements immediately associated therewith. In Fig. 2 the blocks 48 are clearly shown and it will be seen that carried by each of these blocks is a smaller bearing block 68 each of which holds a pivot pin 62, the inner end of each of which is fixed in one of the two bosses 64 of the gimbal ring 65. The axes of the pins 62 form the transverse axis X-X, and therefore the gimbal ring 66 is free to pivot about this axis. Also carried by the gimbal ring 66 are the two bearing blocks 68 each of which pivotally holds an additional pivot pin I8, the inner ends of each of which are aflixed to the collimator housing 56 in a manner to be described. The axes of the pins 18 form the longitudinal axis YY, and so the collimator housing 56 is free to pivot about the axis Y-Y with respect to the gimbal ring 68. It will therefore be appreciated that by virtue of this mounting arrangement the collimator housing 46 is 4 universally mounted and therefore may be selectively positioned about either of the two axes as the situation requires.

For purposes which will become more apparent as the description proceeds, it is important that the bearing arrangement just described shall be of the low friction type. Accordingly the following bearing arrangement may be included in my invention to very good advantage, but other lowfriction type bearings may be used.

Reference is now made to Fig. 3 which is a perspective view of either of the two bearing blocks 48 and its associated elements. It will be seen that the bearing block 48 is supported by the guard 58 and by the upright 38, and that the smaller bearing block 68 is aflixed to the larger block 48 by means of screws I2. The block 68 is recessed for the reception of the V-notched agate bearing 14. Integral with the gimbal ring 68 is the boss 64 which holds the pivot pin 62 by means of the set screw 18. The lower side of the outer end of pivot pin 62 is also V-shaped, but the surfaces forming the V-shaped end of pin 62 form a smaller angle than do the surfaces which form the V-notch in bearing 14. Accordingly, the lower surface 88 of pin 62 rests upon the lower surface 82 of the bearing I4, forming a knife-edge bearing having extremely low friction. A cap 84 may be attached by screws 86 passing through the holes 88 and 98, the latter being tapped, to prevent lifting of the pivot pin 62 from the agate bearing I4.

Accordingly, because of the provision of the two assemblies illustrated in Fig. 3, the location of which is shown in Fig. 2, the gimbal ring 66 may be very delicately balanced about the transverse axis XX.

Similar assemblies like that shown in Fig. 3 are provided in order that the collimator housing 56 may also be delicately balanced about the longitudinal axis YY. The exact construction of these latter bearing assemblies is illustrated in Fig. 4, both of the assemblies being identical.

Referring to Fig. 4, the gimbal ring 86 is shown r as is the block 68 which is fixedly attached thereto by means of screws 92. The block 68 is recessed to hold the agate bearing 94 in the same manner as described in connection with Fig. 3. This bearing has a V-notch 96 like those previously described, and a cap 88 is provided to hold the outer end of pin '58 in position with respect to the agate bearing 9 The outer end of pin I8 also has a V shape so that the outer end of pin I8 and agate bearing 84 provide a knifeedge bearing surface, all as previously explained. The inner end of the pivot pin it is fixedly held by the block 582 by means of the set screw I84. Placed inside the housing of the collimator assembly are two frame members I86 which extend, in a horizontal plane, completely around the interior of the four vertical Walls 56a, 56b. 58c and 56d of the collimator housing 56. These frame members I66 form a part of the tubular frame work inside housing the frame also comprising the four vertical corner members I87, a plurality of horizontal members E88, and a plu rality of angular members I89, as seen in Fig. 6. The side Walls, top and bottom of housing 56 may be attached to the frame members in any desired The block 32 fits snugly between the two frame members I86 and is suitably rigidly afilxed thereto by any suitable means.

It will therefore be appreciated that the two provided assemblies like the one disclosed in Fig. 4 allow easy movement of the collimator aerated housing 56 about the longitudinal axis Y'-Y, the collimator housing being delicately balanced about this axis.

Accordingly, the collimator housing 56 is delicately balanced about the axes X-X and Y--Y. Means are also provided for damping the action about both of these axes in order to prevent rapid and excessive oscillation of the collimator assembly when it is being moved by the student about the vertical axis of spindle I2, which movement, as previously explained, may be produced by means of the handle 53. The means for damping the oscillation of the collimator assembly 46 about the axis Y-Y are disclosed in Fig. 5, to which reference is now made.

In Fig. 5 it will be seen that the vertical wall 56d of the collimator housing is shown. Trian gular shaped bracket H6 having two angularly disposed supporting members I i2 is provided, this bracket being affixed to wall 5601 by means or" screws lit. Integrally formed with the bottom IE6 of bracket lid is the depending projection I I3 which is transversely drilled to allow the pin E26 to pass therethrough. A pair of brackets it? including the angularly disposed supporting members 524 are affixed to gimbal ring 66 by means or" screws I26, and these two brackets support the plate 528 by means of the bolt and nut arrangements designated generally by l36. Plate IE8 in turn supports the dashpot 432 having the usual cap IM and plunger I36. The upper end of plunger i536 has formed integrally therewith the enlarged threaded portion I38 which coacts with the internally threaded knurled member 543. A threaded member hi2 also enters the upper side of member Hi6 and the upper end of member M2 is affixed to the coupling I44 which isslotted at M6 for the reception oi the depending member II8, coupling wi l also being drilled transversely for the reception of pin I26. Accordingly, coupling Hi l is pivotally attached to the depending memer H8 oi part H6 of. bracket H6. The location of dashpot iSZ and of bracket members H2 and I56 is shown in Fig. 2. It will be appreciated, considering Figs. 2 and 5, that the dashpot assembly in Fig. 5 damps the oscillation of the collimator assembly 46 about the longitudinal axis Y-Y. The adjusting nut I46 of the assembly shown in Fig. 5 may be used in order to adjust the action or" the dashpot assemblies, as occasion requires. Preferably, the assembly is adjusted to the near critical point.

In Fig. 6 the dashpot assembly designated generally by its is shown. This assembly may be substantially like the assembly show in Fig. 5, except that it has an upper bracket I46 affixed to the gimbal ring IE6 instead of to the housing 56 as is the upper bracket of the assembly shown in Fig. 5. The dashpot assembly M6 also includes a dashpot I56 like the dashpot it?! in Fig. 5, dashpot 356 being held by the fixed guard 56. The plunger of dashpot I56 is numbered I5l, an adjusting nut lot is provided, and threaded link B53 interconnects nut I52 and bracket M6, ex-- actly as shown in Fig. 5. Except for the fact that the dashpot assembly I46 is mounted with respect to the gimbal 66 and fixed guard 56, instead of with respect to the collimator housing 56 and gimbal 56, assembly M6 may be like that shown in Fig. 5. Accordingly, it will be appreciated that the dashpot assembly I46 damps the oscilIation of the collimator housing 56 and gimbal 6t about the transverse axis XX. The dashpot assembly I46 may be adjustedas required by means of hut I52.

Still referring to Fig. 6-, the bottom 56f or the collimator assembly-46 is shown, and resting upon this bottom is the weight I56. It will be noted in Fig. 6 that weight I56 runs longitudinally of the collimator housing. Referring to Fig. '7, the bottom 56] and weight I56 are shown, and it will be seen that a slot I56 also runs longitudinally of the bottom I54. A bolt I66 passes through weight I56 and may pass through the slot I56, a nut I62 being provided for engaging the lower side of bottom 56] in order to hold the bolt I66 and weight I56 in the desired position. By virtoe of this arrangement, it will be appreciated that the weight I56 may be slid longitudinally of the bottom 56 in order to adjust the entire collimato'r housing 56 about the transverse axis X=X.

Also seen Fig. 6 is a second weight I64 which rests transversely upon the bottom 56 of the collimator housing, and referring to Fig. 7 it will be seen that a second slot I66 extends transversely of the bottom SW. A bolt I68 passes through weight I64 and may pass through the slot I66, a nut I76 being provided to engage the lower threaded end of bolt I63} hut I16 being under the bottom 66 of the housing. By virtue of this arrangement it will be appreciated that the weight I64 may be positioned transversely of the bottom or the collimator housing in order to adjust the position of the housing about the longitudinal axis Y-Y.

In Fig. 6 it will be seen that a fixed weight I12- ls carried by the collimator assembly in order to generally balance the assembly about the transverse axis X-X. In Figs. 1 and 2 a shot cup H5 is fixed upon the leit side 5% oi the collimator housing 56. This cup is provided in order that small metal pellets may be selectively placed therein in order to delicately balance the collimator assembly 46 about the longitudinal axis Y--Y. In Figs. 2 and 6 it will be seen that a similar cup H6 is mounted upon the rear side 56a of housing 56 in order that the collimator housing may be delicately balanced about the 45 transverse axis XX by the use of metal pellets put in or removed from the cu as the case requires.

The provision or the heavy fixed weights in the bottom of housing 56 provides a pendulous struc- 50 ture which will accurately reposition itself about the axes X'- X and Y- Y.

Turning now to a discussion of the optical system of the invention being disclosed herein, in Fig. 6 it will be Seeri that four lamps I18 are suitably mounted within the lamp housing I86 which rests upon the bottom 56 of the collimator housing 56. Within the housing 56 is suitably placed a horizontally disposed plate assembly frame I82 which holds the plate assembly designated gen- 50 erally by I84. Referring to Fig. 8 it will be seen that the plate assembly I64 includes three plates I66, I88, and I60. The plate I86 is a blue filter plate, the plate I88 is an opal glass plate, and the plate I 96 is the horizon image plate. 65 These three glass plates are separated by suitable felt padding I512. The blue filter plate cuts down the red light emanated by the lamps I76 so that the image will be more normally colored in appearance, as will later appear. The opal glass 70 plate diffuses the light before it reaches the lower surface of thehorizon image plate. The horizon image plate is preferably a blue dye-coupled, dial-positive print of an ocean horizon photographed on an emulsion coated dry plate. The first twoaol-ateszmay be fixedly held by the frame member 532, but the horizon image plate I90 may be Slightly smaller in size than the dimensions of the frame M2 to permit adjustment thereof in relation to the other parts of the optical system, for reasons which will become readily apparent. Plate I90 may be held in position by clamps 593. Reference is made to Fig. 9 which shows the horizon plate I90, the lower darker portion Hilda of this plate having a water-like appearance, the upper lighter portion 19% hava sky-like appearance, and the two portions forming a linear horizon-like line I900.

Positioned in the top of the collimator housing is the angularly disposed transparent reflector 202 which is held by the frame 204 which in turn is held by the framework I06 of the collimator housing. Framework I09 is shown in Fig. 4. Positioned in the rear of the housing 56 at the upper end thereof is the spherical first surface concave collimating mirror 206, held by the frame member 208 which in turn is fixedly attached to the transverse frame members I08. Upon the other side of the collimator is the viewing window 58 which has been previously mentioned, this window being held by the circular frame member 2 It which in turn is held by screws 2i2 to the front wall of the collimator assembly.

The transparent reflecting mirror 202 is mounted at an angle of 45 degrees to the vertical axis of housing 56, and may be preferably made of optically fiat planoparallel plate glass, having a -ansparent high reflectance coating on the lower surface and a low reflectance coating on the upper surface. By employing these coatings,

one of the double images of the horizon line will be greatly diminished in intensity and the other will be increased in intensity so that no confusion will result upon the part of the observer as to which horizon image should be selected for leveling the sextant.

The window 58 has a low reflectance coating on both sides.

Any point I900 upon the horizon line I90 may be selected, and it will be seen that diverging rays emanating from this point strike the transparent reflector 202 and are reflected toward the collimator 2%. The rays will be collimated, or rendered parallel, by the mirror 206 and reflected back through the transparent reflector 202 and window 59 and will be seen at the point P. Inasmuch as all rays from the point I900 are parallel at the point P, it will be appreciated that the point E900 appears to be at infinity. Inasmuch as point 8990 may be selected at random, and the horizon line I 900 is composed of an infinite number of such points, the entire horizon line 5560 appears to be located at an infinite distance. Similarly, the diverging rays from any point I90b which is located on any part I 902) of the plate 90 which represents the sky strike the transparent reflector 292, are reflected to the collimator 206, are collimated and reflected back through the transparent reflector 202 and window 50 to the point P. Accordingly all light rays from the point IEQb which pass through the point P are parallel, so that the point I901) upon the plate appears to be at infinity. Inasmuch as point I902), in the illustrative case, was selected at random, and the sky portion I90?) of plate I90 is composed of an infinite number of such points, all the sky portion i992) appears to be at infinity.

At the same time, the diverging light rays from any point I90a upon the part I90a of the plate I90 which represents the water also strike the transparent reflector 202, are reflected to the collimating mirror 206, and are there reflected back through the transparent reflector 202.

Reference is now made to Figs. 10 and 11 which disclose diagrammatically the optical principles of our just described optical arrangement. The plate 90 is shown, as is the transparent reflector 223-2 and the collimator 206. Any point I900, in Fig. 10, upon the horizon line may be selected, and it will be seen that diverging rays emanating from this point strike the transparent reflector 202 and are reflected toward collimator 200. The rays will be collim'ated, or rendered parallel, by the collimator and will be reflected back through the transparent reflector and window 58. Within the limits of the apparatus, no matter where the eye is placed all rays from the selected point upon the horizon are parallel and the point appears to be at infinity. Accordingly, all such points upon the horizon line similarly appear to be located at infinity, and so the horizon image appears to be located at infinity.

A similar optical diagram, it will be appreciated, can be prepared to illustrate that the same would be true of any point selected upon the sky portion Ib or water portion I90a.

Referring to Fig. 10A, it should be particularly noted that the light rays intercepted by the eye from the portion of the plate I902) which represents the sky are not parallel with the light rays from the horizon line I900 or from the water portion I'90a. The light rays from the sky portion 9979 are reflected downwardly from the collimator 206, and therefore the proper illusion is obtain d. The light rays from the horizon line Who are generally parallel with true horizontal, thus preserving the proper illusion, and the light rays from the water portion I90a are inclined upwardly to produce the same effect. The same rules apply to light rays from the different parts of the sky portion I901), different parts of the horizon line I900, and different parts of the water portion I90a. It will therefore be appreciated that with the explained optical arrangement, not only are all light rays from any given point upon the plate I90 parallel to one another when intercepted by the eye, giving the illusion that the scene is at an infinite distance, but the proper angles are obtained between the parallel rays from each point with respect to the parallel rays of all other points so that a proper sky, horizon and water scene impression is obtained. This impression is illustrated in Fig. 11.

In view of the type of image, as shown in Fig. 11, produced by the apparatus previously explained, it will be appreciated that the apparatus of this invention may be placed out-of-doors and that practice may be secured by means of the use of a sextant equipped with a horizon viewing arrangement, in conjunction with the apparatus of this invention, in taking observations upon the stars, sun, moon and other planets. By means of the handle 54 shown in Fig. 1, the collimator assembly may be positioned so that an observation upon any selected star or planet may be taken, regardless of the azimuth of the star from the location of the apparatus. The horizon image is sighted with the sextant, just as in actual practice, and the image of the celestial body being observed is brought into coincidence with the image of the horizon line, in the conventional manner,

In order that this invention may be adaptable to various types of lighting conditions-for example day or night, cloudy, etc.encountered dur-.

ing its use, the following means may be incorporated in order that the illumination of the plate I98, and consequently the intensity of the viewed image, may be regulated as desired. As seen in Fig. 1, a box 229 is fixedly mounted upon the side of the housing 56, and this box has mounted upon its face a scale 2.22. This scale may simply contain directions concerning the direction in which the knob 224 carried by the box must be rotated in order to increase or decrease the illumination of the plate I98. Referring now to Fig. 12, it will be seen that the lamps I18 are connected in parallel by means of con- .ductors 226 across one of the terminals of the Variac or auto-transformer 228 and the rotor 224a of this transformer. The two fixed terminals of the transformer 228 are connected through slip rings 2!, brushes 23, conductors 230 and switch 23!, the location of which is seen in Fig. 1, to a suitable source of current. The rotor 224a .of transformer 228 is under the control of knob 224, shown in Fig. 1. It will be appreciated therefore that the observer may, by rotating knob 22.4, position the rotor 224a to regulate the voltage across lamps I18, thereby regulating the intensity of the illumination of plate I90, and accordingly, the intensity of the viewed image.

In order that the apparatus of this invention may be adjusted to practice the taking of observations from different heights above the horizon, the following means are incorporated. Referring to Figs. 1 and 13. it will be seen that a scale 232 is aiiixed to the side 5612 of the collimator housing by means of screws 234. This scale may bear suitable graduations in terms of assumed height above the water level, in the illustrated case ll, 20, 45 and I89. Below scale 232 is mounted the bar 235 which is ofiset from the side 561) by means of blocks 238, bolts 24.8 holding the bar 236 and blocks 238 in position. A slidable weight 242 having an integral pointer 242a is mounted upon the bar 23 8 for movement therealong. It will be appreciated that as the weight 242 is moved from the 8 end toward the I88 end, the entire horizon collimator assembly 48 will be moved about the transverse axis X-X. The angular amount of this movement will be dependent upon the distance which the weight is moved. As the weight moves toward the Hi8 end, it will be appreciated that the moments are changed so that the bottom end of the collimator assembly moves ahead and the upper end to the rear. Referring to Figs. 10 and 10A it will be appreciated that this movement of the collimator assembly will result in a shifting of the entire optical system so that the rays of parallel light from all the various points along the horizon line 1960 passing through the point P are inclined upwardly to a greater extent to form a larger angle with the horizontal. Accordingly the reading obtained by the use of the apparatus of this invention will show the altitude of the star being observed as being greater. This exactly parallels the case when viewing the real horizon to level the sextant while taking .an observation, as the distance above the real horizon increases, The observer may correct for dip accordingly. Movement of the weight 242 in the opposite direction would, of course, have the opposite effect, and is done whenever it is desired to simulate the taking of observations from a lower height above the water. When the pointer 242a is in the .8 position, in Fi 1.0 the parallel rays from the horizon line 19110 are parallel to the true horizontal.

.As previously stated, the apparatus of this invention ma also b u i c njunction wit training devices of the type disclosed in U. S. Patent 2,364,539 issued to Edwin A. Link. In order to illustrate this use .of the apparatus of this invention, reference is made to Fig. 14 where certain parts of the apparatus of that patent are disclosed. In Fig. 14 the main steel framework of such a trainer comprises four main upright posts 250, a plurality of transverse supporting members 252, as well as a plurality of angularly disposed supporting members 254. The upper framework is generally designated by 256, and need not be described in detail.

The conventional dome rail is designated 258, the lower end of this rail being held by the steel plate 260, and the upper end is held by the steelworl; designated generally by 260. The dome gear box is numbered 264 and this gear box is supported upon the rail 258 by means of lugs 266. The dome is designated generally by 268, and includes, generally, a pair of outer hoops 21.8 as well as a plurality of arcuately shaped ribs 212, the lower ends ofwhich are affixed to the hoops 21.0, and the upper ends of which are atfixed to the main hub 214. Attached to the inside of the dome is the mesh wiring 218 upon which are mounted a plurality of light sources 280 which represent the non-navigational stars. A plurality of collimators 282 are carried by the ribs 212, these collimators representing the navigational stars upon which sextant observations are made by the student who is receiving practice in the use of the trainer. The collimators 282 may be ,of the type covered by U. S. Patent 2,310,- 031 issued Februa y 2, 1943 to Gunne Lowkrantz.

An .operators desk 284 is provided having a panel 286 which holds an instrument panel 288. A plurality of instruments 290 are held by the instrument panel. A gooseneck 292 forms a part of the apparatus, this g-ooseneck holding the light 294 as well as the cable 295 which is connected to the control apparatus of the recorder or flight simulating device 298 in order to control the. movements of the latter over chart 300. Device 298 is disclosed and claimed in U. S. Patent 2,179,- 663 issued December ,5, 1944, to Edwin A. Link.

All of the preceding described apparatus shown in Fig. 14 is completely disclosed in detail in the above mentioned Patent 2,364,539, issued to Edwin A. Link, and forms no part, in and of itself, of the present invention. It is sufficient to state that the instructor positioned at the desk 284 is provided with controls in drawer 284a to move the dome gear box 264 along the dome rail 258 so that the entire dome assembly 258 is tilted with respect to the students observation point according to the instant assumed latitude at which they student is located. Also, the entire dome assembly 268 may be rotated about an axis through the hub 214 in accordance with the instant assumed local hour angle of Aries which depends in turn upon the combined factors of instant assumed time and instant assumed longitude. Accordingly the instructor may position the entire dome assembly 268 so that the student may take observations upon any of the stars represented by the collimators 28,2, and if the observations are properly taken the reading obtained by the student will be the same as the reading he would secure if he were actually Observing the real star represented by the collimator in question at a longitude, latitude and time corresponding to the basic assumed factors, In this manner, the student, knowing the ,asumed time and the star upon which it is assumed he is taking an observation,

1 I will be able to calculate his assumed latitude and longitude.

Also seen in Fig. 14 is the collimator assembly and many of its associated parts, all numbered as previously described. Around the platform 26 upon which the student stands is a larger stationary platform 302 which may be mounted by means of steps 3%. The apparatus of this invention is placed, when used in conjunction with training devices of the type just described, so that the student may place his sextant in the area at which the rays from each of the collimators 232 intersect, and at the same time view the rays emanating from the collimator assembl 45 through window 58. In this manner the student may use th apparatus of this invention to level his sextant, and instead of observing the actual stars he ma observe the stars represented by the collimators 282.

When so used the position of the recorder 298 may indicate with respect to chart 300 the assumed position of a water-borne vessel, and the movements of recorder 298 may be controlled by the instructor in accordance with the instant assumed factors of ship heading, ship speed, and ocean current and direction. These factors may be integrated in a manner Well known to those skilled in the art of synthetic training devices, as by use of the instrument disclosed in the patent application of Gunne Lowkrantz and Karl A. Kail, Serial Number 406,056, filed August 8, 1941, for Wind drift instrument.

Such an instrument is shown in Fig. 14 and is designated 3l5. It has a ship speed control M5, a ship heading control 3 l1, an ocean current speed control 3|8, and an ocean current direction control 3l9, all connected to the instrument 3I5 in a manner clear to those skilled in the art.

Reference is now made to Fig. 14 where the box 320 is shown mounted upon the platform 3B2, this box having a window 322 in the top thereof. In Fig. 15 it will be seen that contained in the box is a model ship 324 which may be rotatably mounted in any desired manner. The ship 32 represents the ship upon which the student is assumed to be located, when the arrangement shown in Fig. 14 is employed, and by reference thereto and to the dome 268 the student may ascertain in what position the collimator assembly 46 must be placed to make an observation upon the collimators 2B2 assumed to be off the stern, bow or abeam the ship.

If desired the ship model 324 may be rotated by the instructor at desk 284 by the well known Selsyn-type transmitting systems, such as widely used in the field of synthetic training devices, and this Selsyn transmittin system may be operated by the same control 3|! used by the instructor to introduce into the wind drift instrument the factor of assumed ship heading.

As another example to illustrate the wide use of the apparatus of this invention, the apparatus shown in Fig. 1 may be mounted with respect to an artificial star in the form of a single collimator, and practice may be secured in taking observations with the use of a marine sextant.

The collimator housing 56 may be positioned by means of the adjustable weights previously described so that when the weight 2 t2 seen in Fig. 13 is in th ll position the horizon image will coincide with the horizontal cross-hair of a transit level when the transit level is at zero altitude.

It will be appreciated by those skilled in the art that many changes may be made in the construction of this invention without departing from the substance thereof. Also, other uses for this invention ma be found by those skilled in the art. All such changes and all such uses are intended to be covered by the following claims.

We claim:

1. In a device for simulating the natural horizon the combination of a housing having a side, a frame member for holding said housing, universal mounting means interconnecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about two mutually perpendicular axes passing through said housing above the center of gravity thereof, a source of illumination in said housing, an image carrying member in said housing arranged to be illuminated by said source of illumination, said image carrying member including a linear mark representative of the horizon, a transparent reflector in said housing, a collimatin reflector on one side of said transparent reflector and a viewing window in the said side of said housing on the opposite side of said transparent reflector and extending parallel to said linear mark, said image carrying member, said transparent reflector, said collimatin reflector and said viewing window all being arranged so that light rays from said linear mark are reflected by said transparent reflector to said collimating reflector which renders the rays from any point on said mark substantially parallel and reflects them through said transparent reflector and horizontally through the viewing window to form a horizontal image of said mark at approximate optical infinity.

2. In a device for simulating the natural horizon the combination of a housing having a side, a frame member for holding said housing, universal mounting means interconnecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about two mutually perpendicular axes passing through said housing above the center of gravity thereof, movable means carried by said housing for adjusting the balance thereof about each of said axes, a source of iilumination in said housing, an image carrying member in said housing arranged to be illuminated by said source of illumination, said image carrying member including a linear mark representative of the horizon, a transparent reflector in said housing, a collimating reflector on one side of said transparent reflector and a viewing Window in the said side of said housing on the opposite side of said transparent reflector and extending parallel to said linear mark, said image carrying member, said transparent reflector, said collimating reflector and said viewing window all being arranged so that light rays from said linear mark are reflected by said transparent reflector to said collimatin reflector which renders the rays from any point on said mark substantialy parallel and reflects them through said transparent reflector and horizontally through said viewing window to form a horizontal image of said mark at approximate optical infinity.

3. In a device for simulating the natural horizon the combination of a housing having a side, a frame member for holding said housing, universal mounting means interconnecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about two mutualy perpendicular axes passing through said housing above the center of gravity thereof, movable means carried by said housing for adjusting the balance thereof about each of said axes, a source of illumination in said housing, an image carrying member in said housi-ng arranged to be illuminated by said source of illumination, said image carrying member including a linear mark representative of the horizon, a transparent reflector in said housing, a collimating reflector on one side of said transparent reflector and a viewing window in the said side of said housing on the opposite side of said trans parent reflector and extending parallel to said linear mark, said image carrying member, said transparent reflector, said collimating reflector and said viewing window all being arranged so that diverging light rays from any one of several selected points on said linear mark are reflected by said transparent reflector to said collimating reflector which renders the rays from any one of said points substantially parallel and reflects them through said transparent reflector and horizontally through said viewing window, the said same elements also being arranged so that the parallel rays from any one of said points are reflected by said collimating reflector converging with respect to the parallel rays from any other point to form a horizontal linear image of said linear mark at approximate optical infinity.

4. In a device for simulating the natura1 horizon the combination of a housing having a side, a frame member for holding said housing, universal mounting means inter-connecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about its mutually perpendicular longitudinal and transverse axes passing through said housing above the center of gravity thereof, a weight carried by said housing and movable with respect thereto to change the position of said housing about its transverse axis, indicating means carried by said housing for indicating in predetermined terms the effective displacement of said weight from a predetermined position, a source of illumination in said housing, an image carrying member in said housing arranged to be illuminated by said source of illumination, said image carrying member including a transverse linear mark representative of the horizon, a transparent reflector in said housing, a collimating reflector on one side of said transparent reflector and a viewing window in the side of said housing on the opposite side of said transparent reflector and extending parallel to said linear mark, said image carrying member, said transparent reflector, said collimating reflector and said viewing window all being arranged so that light rays from said linear mark are reflected by said transparent reflector to said collimating reflector which renders the rays from any point on said mark substantially parallel and reflects them through said transparent reflector and horizontally through the viewin window to form a horizontal image of said mark at approximate optical infinity.

5. In a device for simulating the natural horizon the combination of a fixed base, a frame member rotatably held by said base for rotation about a vertical axis, a housing having a side, universal mounting means interconnecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about two mutually perpendicular axes passing through said housing above the center of gravity thereof, a source of illumination in said housing, an image carrying member in said housing arranged to be illuminated by said source of illumination, said image carrying member including a linear mark representative of the horizon, a transparent reflector in said housing, a collimating reflector onone side of said transparent reflector and a viewing window in the said side of said housing on the opposite side of said transparent reflector and extending parallel to said linear mark, said image carrying member, said transparent reflector, said collimating reflector and said viewing window all being arranged so that light rays from said linear mark are reflected by said transparent reflector to said collimating reflector which renders the rays from any point on said mark substantially parallel and reflects them through said transparent reflector and horizontally through the viewing window to form a horizontal image of said mark at approximate optical infinity,

6. In a device for simulating the natural horizon the combination of a fixed base, a vertical spindle supported by said base, a platform held by the top of said vertical spindle, a sleeve supported by said base surrounding said vertical spindle and separated therefrom, frame means rotatably carried by said sleeve, a housing having a side, universal mounting means interconnecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about two mutually perpendicular axes passing through said housing above the center of gravity thereof, a source of illumination in said housing, an image carrying member in said housing arranged to be illuminated by said source of illumination, said image carrying member including a linear mark representing the horizon, a transparent reflector in said housing, a collimating reflector on one side of said transparent reflector and a viewing window in the side of said housing on the opposite side of said transparent reflector and extendin parallel to said mark, said image carrying member, said transparent reflector, said collimating reflector and said viewing window all being arranged so that light rays from said linear mark are reflected by said transparent reflector to said collimating reflector which renders the rays from any point on the mark substantially parallel and reflects them through. said transparent reflector and horizontally through the viewing window to form a horizontal image of said mark at approximate optical infinity.

'7. In a device for simulating the natural horizon the combination of a housing having a side, a frame member for holding said housing, universal mounting means interconnecting said frame member and said housing whereby said housing is mounted for movement with respect to said frame member about two mutually perpendicular axes passing through said housing above the center of gravity thereof, movable means carried by said housing for adjusting the balance thereof about each of said axes, a source of illumination in said housing, an image carrying member in said housing arranged to be illuminated by said source of illumination, said image carrying member including a linear mark representing the horizon, a transparent reflector in said housing, a collimating reflector on one side of said transparent reflector and a viewing window in the said side of said housing on the opposite side of said transparent reflector and extending parallel to said mark, said image carrying member, said transparent reflector, said collimating reflector and said viewing window all being arranged so REFERENCES CITED The following refernlces are of record in the file of this patent:

Number Number 16 UNITED STATES PATENTS Name Date Pedersen Apr. 10, 1917 Morton Jan. 29, 1924 Crane et a1 Sept. 1, 1936 Hutter June 20, 1944 Chwalow Sept, 19, 1944 MacGill Dec. 5, 1944 Link Sept. 18, 1945 FOREIGN PATENTS Country Date France May 24, 1909 Great Britain May 14, 1925 

